Low-pressure mercury-vapor gas-discharge fluorescent lamp with amalgam

ABSTRACT

A low-pressure mercury-vapor gas-discharge fluorescent lamp contains an amalgam of the formulation: MERCURY 15-20 AT. PER CENT LEAD 45-75 AT. PER CENT BISMUTH 40-05 AT. PER CENT ENSURING AN OPTIMUM LUMINOUS FLUX IN THE TEMPERATURE RANGE FROM 10* TO 35* C. and preventing the escape of mercury into the surrounding premises.

United States Patent Shindelman et a].

[54] LOW-PRESSURE MERCURY VAPOR GAS-DISCHARGE FLUORESCENT LAMP WITH AMALGAM [72] Inventors: Jury losifovich Shindelman, ulitsa Kalinina, 3, kv. 57; Galina Iosifovna Akulova, ulitsa Tsiolkovskogo, 37, kv. 63, both of Poltava, USSR.

22 Filed: April 8, 1971 [2]] Appl.No.: 132,392

[30] Foreign Application Priority Data May 25, 1970 U.S.S.R. ..14299ll [52] US. Cl. "313/109, 3l3/l74,'3l3/l79 [5 1] Int. Cl ..H01j 61/24 [58] Field of Search ..3l3/l09, 174, 178,179

[56] References Cited UNITED STATES PATENTS 3,152,278 10/1964 Dziergwa et al. ..313/l09 X 451 Aug. 8, 1972 Dziergwa et al ..313/l79 Evans et al. ..3l3/l74 Primary Examiner-Roy Lake Assistant Examiner-Palmer C. Demeo Attorney-Holman & Stern ABSTRACT mercury 15-20 at. per cent lead ..4575 at. per cent bismuth 40-05 at. per cent ensuring an optimum luminous flux in the temperature range from 10 to 35 C. and preventing the escape of mercury into the surrounding premises.

1 Claim, 1 Drawing Figure LOW-PRESSURE MERCURY-VAPOR GAS- DISCHARGE FLUORESCENT LAMP WITH AMALGAM The present invention relates to electric gasdischarge lamps, and more specifically to low-pressure mercury-vapor gas-discharge fluorescent lamps with an amalgam.

In the prior art, there are low-pressure mercuryvapor gas-discharge fluorescent lamps using bi-component amalgams (cadmium-mercury, indium-mercury, thallium-mercury, and the like), tri-component amalgams (cadmium-tin-mercury, cadmium-bismuthmercury, indium-zinc-mercury, indium-thallium-mercury, and so on), and tetra-component amalgams (indium-cadmium-tin-mercury), which are pastes or, though seldom, hard alloys.

A major disadvantage of prior-art mercury-vapor gas-discharge fluorescent lamps using theabove-listed amalgams is that they would produce a maximum of luminous output at a temperature above 30 C., which is beyond the operating limit for most low-pressure fluorescent lamps.

This disadvantage is mainly traceable to the low partial pressure of the mercury vapor over the amalgam at temperatures below 30 C., because of which the resonance radiation responsible for the excitation of the phosphor is low in intensity.

This implies that low-pressure mercury-vapor gasdischarge fluorescent lamps with prior-art amalgams are unsuitable for operation at ambient temperature below 30 C. As an alternative, use might be made of mercury, a scarce and highly toxic material, which is likewise undesirable.

It is an object of the present invention to avoid these disadvantages.

Another object of the invention is to provide a solid amalgam composition ensuring optimum performance for low pressure mercury-vapor gas-discharge fluorescent lamps at ambient temperatures below 30 C. by the proper choice of the amalgam formulation, this amalgam being suitable for lamps of any power rating and independent of the manner in which it may be disposed in a lamp.

With these objects in view, the present invention resides in that, in a mercury-vapor gas-discharge fluorescent lamp, use is made of an amalgam of the formulation: mercury, at. per cent; lead, 45 75 at. per cent; bismuth, 4O 05 at. per cent, ensuring an optimum lumnious flux in the temperature range from 10 to 35 C.

This is a solid amalgam with a melting point of 200 to 220 C., possessing sufficient plasticity such that it can be manufactured into any shapes (such as bars, pellets, balls, hollow cylinders, and the like or made in the form of a powder) and introduced into mercury-vapor gas-discharge fluorescent lamps in any desired amounts.

Since mercury is extremely inactive under normal conditions, the amount of amalgam introduced into a lamp ensures optimum performance and at the same time prevents any contamination of the production premises with mercury.

Placement of the amalgam in a lamp is not critical,

The invention will be more fully understood from the following description of preferred embodiments when read in conjunction with the accompanying drawing which shows a plot relating the luminous flux of a 40-W mercury-vapor gas-discharge fluorescent lamp using various amalgam formulations, to ambient temperature.

These curves (A, B, and C) illustrate the performance of a mercury-vapor gas-discharge fluorescent lamp in which the amalgam has varying percentages of mercury, bismuth, and lead. The formulations of the respective amalgams introduced in the lamp are summarized in Table 1.

TABLE 1 Ingredient, Curve at. A B C Mercury (Hg) 20 20 l5 Bismuth (Bi) 20 5 10 Lead (Pb) 75 Total at. 100 at. I00 at.

Referring to the plot, curves A, B, and C are seen to have all a single peak in the temperature range from 30 to 35 C. The most attractive formulation appears to be the one containing 20 at. per cent mercury, 5 at. per cent bismuth, and 75 at per cent lead, because its luminous flux decreases gradually on moving into the region of higher temperatures. The yield of mercury vapor from the amalgam is mainly decided by its content of lead which acts as a kind of stabilizer of an optimum pressure of mercury vapor (3 X 10* mm Hg) in the lamp. Partly, the maintenance of this optimum pressure of mercury vapor is due to the formation of intermetallic mercury-bismuth compounds. In contrast to the classical chemical bonds ion and covalent, these compounds feature a specific metallic bond which invalidates the valence theory.

When a lamp is burning, the thermal effect on the amalgam results in that the intermetallic mercurybismuth compound breaks up, thereby supplying a further amount of mercury vapor in the lamp.

Since the pressure of mercury vapor over this type of amalgam at 20 C. does not exceed 10' mm Hg, the escape of mercury into the surrounding premises is completely prevented.

The amalgam is prepared from inexpensive and abundant materials and compares favorably with any of prior-art amalgams for gas-discharge lamps in cost, low toxicity and superior performance.

The lead of the amalgam only acts as a stabilizer of mercury-vapor yield and does not form any compounds with the mercury.

For comparison, the accompanying plot contains a curve, D, for a fluorescent lamp of equal power rating, using mercury.

What is claimed is:

1. In a low-pressure, mercury-vapor, gas-discharge, fluorescent lamp containing an amalgam, the improvement comprising of the formulation:

mercury 15-20 atom an amalgam per cent lead 45-75 atom per cent bismuth 40-05 atom percent,

ensuring an optimum luminous flux in the temperature and the precise choice of the formulation depends on 65 range from 100 to 350 the power rating of the lamp. 

